Method of forming a pipe covering



Oct. 24, 1961 T. KENNEDY, JR 3,005,742

METHOD OF FORMING A PIPE COVERING Filed May 16, 1958 INVENTOR.

W BY W 5 v United States The present invention relates to an improvedmethod of forming a wrapped covering for pipes, conduits, and likestructures which are installed underground, hence subject ater masticcondition preceding the application of the covering 12. Coating compound14 may be a known bituminous, petroleum wax, or other adhesivecomposition having desired rust inhibitors and wetting agents. Suchwaxes 5 are well known in the art, possessing excellent corrosion toattack or deteriorative action by chemicals, fungi or known syntheticplastic or resin film, such as polyethylother conditions or elementspresent in the soil. The method produces a continuous dielectric shieldfor the pipe which is proof against penetration at the zone of itswrapped overlap.

It is an object of the inventionto pro ideamethodof n coateipipaihehlmrwehtmstripldmayalsohecwn'app ni.

preparing and applying a pipe covering in which a suitable plasticprotective film is wrapped spirally or longitudinally over the pipe,without requiring'any necessary preliminary preparation, and isautogenously sealed in a novel manner to protect the pipe.

Another object is to provide a method as described in which a plasticfilm of known type is spirally or longitudinally wrapped over a bare orappropriately undercoated pipe, and in which overlapped seam zones ofthe film are effectivelyfused andeeaied te em another 'by ae -appar q asze ier the lf desired a saitahle ad an application of appropriatesolvent, so as to provide,

in effect, a continuous, joint-free plastic cover for the A stillfurther object is to provide a method as described, in which the plasticprotective film provides a continuous dielectric shield, proof alsoagainst penetration or deterioration by moisture or chemicals of thesoil, or oil or other fluid carried by the pipe.

Another object is to provide a wrapped pipe covering and method of thesort referred to, in which the protective joint seal at the overlap ofthe Wraps is as permanent as the plastic protective film itself, inwhich the covering can be applied without special preliminarypreparation of the surface of the sealed plastic wrapper, and in whichthe pipe can be lowered into a ditch or trench immediately upon theapplication of the wrapped covering. There is no adhesive or likematerial left at the zone of wrap overlap which is apt to deteriorate.

A still further object is to provide a covering capable of being appliedby a method of dissolving and fusing overlapped seams, in which theapplication of the solvent is made during the operation of wrapping.

The foregoing as well as other objects will become more apparent as thisdescription proceeds, especially when considered in connection with theaccompanying drawing illustrating a preferred embodiment of theinvention, wherein:

FIG. 1 is a fragmentary perspective view, partially broken away,illustrating the improved method of applying a covering to a pipe; and 7FIG. 2 is a view in enlarged scale and transverse section along line 2-2of FIG. 1.

The reference numeral 10 generally designates a pipe or conduit which isto be installed in the ground, bare or coated, to carry oil, gas orother fluids and which is protected against attack and deterioration'asthe result of various conditions, phenomena or elements of the soil bythe covering of the invention, generally designated 12. The referencenumeral 14 designates a coating compound applied to the pipe, in a hotmolten condition or in a cold ene, polyvinylidine chloride,polyvinylchloride, or the like, in a relatively wide size. It is wrappeddirectly on the undercoating either by a spiral wrap as shown orlongitudinally. However, although shown as applied to a on a bare pipe.

In accordance with the invention, as the plastic film strip 16 is woundupon the'coated pipe 10 a suitable solvent 18 for the plastic, such astetrahydrafurane, benzyl 20 alcohol, or methalethyl ketone, is appliedto the lap of the film along which the latter is seamed in wrapping.This solvent may be sprayed, brushed, wiped or otherwise applied on andinto the laps of the primary wrapper 16, and FIG. 1 schematicallydepicts the use of spray hesive additive may be incorporated to enhancethe bond.

As a result theta eatitanstrip l is welded er autog enously fused at theoverlap, providing what is in eifect a continuous plastic cover over thepipe 10. The fused material sets quickly, and the covered pipe may belowered immediately into a ditch after the seal is completed.

The method of the invention provides a continuous dielectric shield forthe pipe, which is also proof against penetration by soil moisture,fungi or chemicals, as well as attack by oil or other fluids handled bythe pipe, which shield is as permanent as the plastic itself. Exposedadhesive material at the laps, such as might deteriorate and defeat thepurpose of the invention, is avoided. The covering can be appliedwithout preliminary preparation of the plastic film, and, as indicatedin 'FIG. 1, the application of the solvent is made in the same operationwith the wrapping.

In this connection, the spray apparatus 20 shown in FIG. 1 of thedrawings may be supported upon pipe wrapping equipment of the typeillustrated and described in my copending application Serial No.735,839, filed May 16, 1958, with the device 20 fixedly disposed at astationery coating location. In the alternative an apparatus in whichthe pipe is held stationary and the wrapping mechanism rotatedtherearound, the spray mechanism 20 the conduit with a flexible tape ofa synthetic resinous plastic material by continuously helically windingthe tape about the conduit with a lead such that each convolutionmarginally overlaps the next preceding convolution in continuouspressure contact therewith so that a continuous seam develops at theoverlap as the convolutions develop, interposing a solvent for theplastic material between the overlapping convolutions by locallyapplying the solvent during winding of the tape as aforesaid to the seamforming margin only of the tape at a point only slightly ahead of thedeveloping seam and moving the V References Cited in the file of thispatent UNITED STATES PATENTS 2,291,838 Shoan Aug. 4, 1942 4 Hosfield MeI 19% 'Ccihvefse Oct. 10, I944 Snyder Feb. 7, 1950 Von Stackelberg Mar.3, 1953 Harder Dec. 11, 1956 Hopkins Apr. 1, 1958

